Ion exchanged glass typically involves immersing a piece of glass into an ion exchange bath. Typically, glass parts are immersed in a hot salt solution, and potassium ions in the solution migrate into the glass surface, replacing the smaller sodium ions originally in the glass. The glass part is then removed from the bath and cooled. As it cools, the larger potassium ions compress the glass and form a tough surface.
To control design complex, stress-varied ion exchanged glass undergoes masking prior to immersion. The masking blocks the ion exchange from a region or region of the glass so it does not become hardened or protected. The masked regions will break easier and allow control where the glass will break. Blocking the ion exchange may also alter the optical properties of the glass.
Currently, masking involves the use of thin films as masks, or complicated gasket systems. These methods may become cost-prohibitive. In addition, the use of gaskets limits the process by temperature and time because the gaskets melt. This limits the amount of time the glass can be immersed in the bath, reducing the effectiveness of the coating that forms in the non-masked regions.